From 4fdee8080912fe6dd76e98526457125e9ee8ec03 Mon Sep 17 00:00:00 2001
From: Gregory LEOCADIE <gregory.leocadie@datadoghq.com>
Date: Wed, 21 Sep 2022 21:25:31 +0200
Subject: Add unw_backtrace2 implementation

---
 include/libunwind-common.h.in |  1 +
 src/mi/backtrace.c            | 33 ++++++++++++++++++++++++++++++---
 2 files changed, 31 insertions(+), 3 deletions(-)

diff --git a/include/libunwind-common.h.in b/include/libunwind-common.h.in
index 9d62aa91..3f04a1c4 100644
--- a/include/libunwind-common.h.in
+++ b/include/libunwind-common.h.in
@@ -316,5 +316,6 @@ extern int unw_get_proc_name_by_ip (unw_addr_space_t, unw_word_t, char *,
 				    size_t, unw_word_t *, void *);
 extern const char *unw_strerror (int);
 extern int unw_backtrace (void **, int);
+extern int unw_backtrace2 (void **, int, unw_context_t*);
 
 extern unw_addr_space_t unw_local_addr_space;
diff --git a/src/mi/backtrace.c b/src/mi/backtrace.c
index b2815137..b6c7457f 100644
--- a/src/mi/backtrace.c
+++ b/src/mi/backtrace.c
@@ -33,15 +33,16 @@ WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.  */
 /* See glibc manual for a description of this function.  */
 
 static ALWAYS_INLINE int
-slow_backtrace (void **buffer, int size, unw_context_t *uc)
+slow_backtrace (void **buffer, int size, unw_context_t *uc, int flag)
 {
   unw_cursor_t cursor;
   unw_word_t ip;
   int n = 0;
 
-  if (unlikely (unw_init_local (&cursor, uc) < 0))
+  if (unlikely (unw_init_local2 (&cursor, uc, flag) < 0))
     return 0;
 
+
   while (unw_step (&cursor) > 0)
     {
       if (n >= size)
@@ -69,7 +70,33 @@ unw_backtrace (void **buffer, int size)
   if (unlikely (tdep_trace (&cursor, buffer, &n) < 0))
     {
       unw_getcontext (&uc);
-      return slow_backtrace (buffer, size, &uc);
+      return slow_backtrace (buffer, size, &uc, 0);
+    }
+
+  return n;
+}
+
+int
+unw_backtrace2 (void **buffer, int size, unw_context_t* uc2)
+{
+  if (size == 0)
+    return 0;
+    
+  if (uc2 == NULL)
+    return unw_backtrace(buffer, size);
+
+  unw_cursor_t cursor;
+  // need to copy, because the context will be modified by tdep_trace
+  unw_context_t uc = *(unw_context_t*)uc2;
+
+  if (unlikely (unw_init_local2 (&cursor, &uc, UNW_INIT_SIGNAL_FRAME) < 0))
+    return 0;
+
+  int n = size;
+
+  if (unlikely (tdep_trace (&cursor, buffer, &n) < 0))
+    {
+      return slow_backtrace (buffer, n, &uc, UNW_INIT_SIGNAL_FRAME);
     }
 
   return n;
-- 
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